Photovoltaic cells or solar cells are photovoltaic components for direct generation of electrical current from sunlight. Due to the growing demand for clean sources of energy, the manufacture of solar cells has expanded dramatically in recent years and continues to expand. Solar cells include a substrate, a back contact layer on the substrate, an absorber layer on the back contact layer, a buffer layer on the absorber layer, and a front contact layer above the buffer layer. The layers can be applied onto the substrate during a deposition process using, for example, sputtering and/or co-evaporation.
Semi-conductive materials are used in the manufacturing or fabrication of at least some known solar cells by being used as the material to form at least a portion of the absorber layer. For example, chalcopyrite based semi-conductive materials, such as copper indium gallium sulfur-selenide (CIGSS) (also known as thin film solar cell materials), are used to complete the formation of the absorber layer after the deposition process. Some techniques that are used for the formation of CIGSS or thin film solar cell materials include a selenization process of metal precursors and a sulfurization process that is conducted after the selenization (the entire process is referred to as sulfurization after selenization (SAS)).
A semiconductor interface, such as a p/n junction, is formed between at least two different types of semiconductor materials of the solar cell substructure. For example, the p/n junction can be formed between two layers of the solar cell such that the p/n junction is buried within the chalcopyrite based semi-conductive materials. Two methods are used to the enhance and/or to facilitate the formation of the p/n junction inside the chalocopyrite based semi-conductive materials. One method is to add a stage during the deposition process, such as during the last stage of the co-evaporation process, for the formation of a surface layer. The surface layer undergoes a copper cation diffusion process for the underlying copper-rich layer and forms a copper-poor layer at the surface. This diffusion process enables the surface layer to have increased cation vacancies that can be beneficial for the later cation diffusion process to form a buried p/n junction. The other method includes the dissolution of a copper metal component of an absorber and the diffusion of a cation, such as cadmium and/or zinc, during a chemical bath deposition (CBD) process.